I noticed holes in the leaves of one of my broccoli plants. Looking on the top and bottom of leaves, I saw no sign of bugs. Days later became an “oh yuck” moment. Shown above are two green worms on a leaf of this broccoli plant in my garden. Those worms are dining on the leaves of the broccoli plant.
Cabbageworm (Pieris rapae)
The green worms are the caterpillar stage of the cabbageworm (also called imported cabbageworm). Cabbageworm, which lives on the leaves of cabbage, cauliflower and broccoli, emerges from off-white colored eggs that are laid on the plant. Within two to three weeks, the green caterpillar larvae are full-grown and turn brown. The full-grown larvae, following a short stay in a silken cocoon, become a white butterfly with black spots.
The cycle starts over again as the adult butterflies look for a location to deposit eggs. Once the eggs are laid on the leaves of cabbage, cauliflower or broccoli, it takes three to seven days for the eggs to hatch, sending small green worms out to feed on the leaves.
I have few plants, so I handpick the larvae off the plants. However, Bt (Bacillus thuringiensis) an insecticide (like Bt Worm and Caterpillar), is a good alternative to kill the worms especially for large plantings of broccoli, cauliflower, or cabbage.
To prevent butterflies from laying eggs on healthy plants, spread row covers over the plants. Another option is to place the foot of a nylon stocking over the developing vegetable head to protect it. I have not tried this approach; supposedly, the stocking stretches as the vegetable head grows.
Hasta la vista, baby
When I enlarged the picture of the worms on this broccoli plant, I noticed black balls near the worms. Could that be larva poop? But wait, it gets worse. The head of the broccoli, shown in the lower right of the picture above, is covered with eggs. On a side note, this picture was taken in early morning and dew drops are clinging to the leaves and to the top of one of the worms.
I pulled the plant and bagged it for the trash. Not a good thing to add to the compost bin.